High Temperature, High Bandwidth Pressure Acquisition System

ABSTRACT

A method, device and system are provided for measuring multiple pressures under severe conditions. In one embodiment, a method comprises receiving, by a processor, from a first sensor, a first pressure signal; receiving, by the processor, from a second sensor, a second pressure signal; receiving, by the processor, from a first memory, a first correction coefficient for the first sensor; receiving, by the processor, from a second memory, a second correction coefficient for the second sensor; modifying, by the processor, the first pressure signal using the first correction coefficient to generate a first corrected pressure signal; modifying, by the processor, the second pressure signal using the second correction coefficient to generate a second corrected pressure signal; and outputting, by the processor, the first corrected pressure signal and the second corrected pressure signal.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §120 to U.S. patentapplication Ser. No. 13/253,139, filed Oct. 5, 2011, which is acontinuation application claiming priority to U.S. patent applicationSer. No. 12/321,521, filed Jan. 22, 2009, now U.S. Pat. No. 8,061,213,issued Nov. 22, 2011, all of which are entitled “HIGH TEMPERATURE, HIGHBANDWIDTH PRESSURE ACQUISITION SYSTEM,” and all of which areincorporated by reference in their entirety as if fully set forth below.

FIELD OF THE INVENTION

The present invention relates to pressure transducer systems and moreparticularly to a system for measuring multiple pressures under severeconditions.

BACKGROUND OF THE INVENTION

There is a need in many applications for measuring a set of pressures ormultiple pressures along a given surface. These measurements, forexample, are made in a wind tunnel where sensors may be placed on thewing of an airplane at different locations. The wind tunnel subjects themodel, such as the wing of an airplane or other model, to extremetemperatures, vibrations and high wind velocity. A common method, whichis employed, is to use a pressure scanner. Such a scanner essentially isa small box with a number of pressure sensors inside. Tubes are run fromthe pressure surface to the scanner in order to measure the pressure. Asone can ascertain, such a device is depicted in U.S. Pat. No. 3,930,412issued on Jan. 6, 1976 to A. D. Kurtz, et al. and entitled “ELECTRICALLYSCANNED PRESSURE TRANSDUCER CONFIGURATIONS.” That patent which isassigned to Kulite Semiconductor Products, Inc., the assignee herein.There is shown a plurality of individual pressure transducers which aremounted or fabricated within a common housing. Each pressure transduceris associated with a separate and distinct pressure port and can besubjected to a different one of a plurality of pressure sensitivelocations to be monitored. The pressure transducers are electricallyscanned by means of a scanning device such as a shift register orcounter so that their individual outputs can be recorded. If one makesreference to the above-noted patent, one will see that the discussion ofwind tunnel measurements is given and various other publications whichare pertinent to such a scanner are also depicted.

While the scanner has been utilized, the disadvantages are that theresponse rate of such a system is greatly lowered because of the factthat long tubes must be run from the scanner module to various pointsalong the wing of an aircraft. As one can ascertain, the wing of anaircraft could be extremely long and therefore the pressure tubes thatare directed from the pressure scanner are long and therefore is verydifficult to get frequency data more than a few tens of hertz. In anyevent, as depicted from the above-noted patent, it has the advantage ofbeing a compact system and does not require a great deal of cabling fromthe scanner to the outside computer system.

Another method of measuring the pressure along a surface is to placeindividual pressure sensors at each measurement point. The output ofeach of these sensors is then directed back to a central dataacquisition system. This configuration has the advantage of allowinghigh frequency data to be taken but it makes the measurement much morecomplicated because the output from each pressure sensor must bedigitally converted and electrical lines must be run from the sensor toa central data acquisition system. This also requires a great deal oftime installing the system as well as retrieving the data from thesystem. In any event, based on the above, it is a object of the presentinvention to provide a pressure system for measuring a multiplicity ofpressures as in a wind tunnel, each under extreme conditions oftemperature and vibration and to enable the system to be simplyimplemented and maintained.

SUMMARY OF THE INVENTION

Apparatus for measuring a plurality of pressures, comprising: aplurality of sensor devices, each capable of providing an output voltageindicative of an applied pressure, with each output voltage having aunique error voltage due to undesirable variations with temperature andpressure, an electronic assembly including multiple inputs each forreceiving an associated output sensor voltage via a single cable fromsaid associated sensor to said associated electronic assembly input, amemory having a plurality of storage locations, with each locationassociated with an associated sensor device for storing thereincompensation values indicative of said error voltage and associated withsaid associated sensor, and processing means located in said electronicassembly and responsive to said sensor output voltages and said storedcomponents for providing outputs indicative of each sensor outputvoltage as compensated by said stored components.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a simple block diagram depicting the pressure acquisitionsystem according to this invention

FIG. 2 is a block diagram depicting an embodiment of the presentinvention.

FIG. 3 is a block diagram depicting an alternate embodiment of thepresent invention.

FIG. 4 is a schematic depiction of a connector configuration employedwith the present invention.

FIG. 5 is a schematic diagram of a pressure sensor bridge circuit usedin this invention.

FIG. 6 is a block diagram of the Acquisition and Compensationelectronics module employed with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, there is a depicted a simple block diagram of apressure system according to the present invention. As seen in FIG. 1,individual transducers such as 10, 11, 12 and 15 are connected viaelectrical lines or cables to a central module 20. The module 20designated as an Acquisition and Compensation electronics 20, andreceives multiple inputs from the pressure sensors as 10, 11, 12 and 15.The pressure sensors, each as indicated, are individual transducerassemblies and are positioned on various points along the model to betested. As indicated above, this may be an aircraft wing or some otherobject which is placed in a wind tunnel. The Acquisition andCompensation electronics 20 digitally converts the data from thetransducers and then compensates the data for various temperatureeffects. The data from each of the sensors, as 10, 11 and so on, canthen be sent on a digital bus 21 to a central computer. An advantage ofthe present system, as will be further explained, is that because eachindividual sensor does not have any compensation they can be made verysmall and made to operate at high temperatures without any loss ofaccuracy. In this manner, a large number of sensors, as 10-15, can beused in a small volume even under extreme environmental conditions. Theelectronics can be mounted in close vicinity but in a much saferenvironment. It is of course desirable to utilize a sensor which can besubjected to high vibration applications and such a sensor, for exampleis described in U.S. Pat. No. 5,955,771, issued on Sep. 21, 1999 to A.D. Kurtz et al. and assigned to the assignee herein. That patent depictsa hermetically sealed sensor device, which has a glass member defining amounting surface and a base surface. The glass member includes one ormore pin apertures extending through the glass member from the mountingsurface to the base. A metallic pin is disposed in each of the pinapertures. The sensor device includes a semiconductor sensor chip,including a semiconductor device and a cover which is bonded and sealedto a surface of the semiconductor device to protect the device from theexternal environment. As indicated, the chip is hermetically bonded andsealed to the mounting surface of the glass member. The semiconductordevice has one or more contacts disposed on the surface and for makingelectrical contact to the device. The portion of each pin extendingabove the mounting surface is received within the contact apertures anda conductive glass frit is disposed in the contact apertures. Thisstructure provides a hermetically sealed sensor device, which is capableof high temperature operation and capable of withstanding high vibrationmodes. As indicated, the above-noted U.S. Pat. No. 5,955,771 isincorporated herein in its entirety and as indicated again, such asensor can be used for sensors depicted as 10, 11, 12 and 15 of FIG. 1.

Referring to FIG. 2, there is shown a first embodiment of the presentinvention. In regard to FIG. 2, the transducers as 10, 11, 12 and 15 arepermanently fixed to the electronic assembly 20, so that each transduceris assigned a fixed channel number in the electronics. In this way thecoefficients for digital correction are programmed into the electronicsand stored there permanently. Both the pressure output and thetemperature of the individual sensors are detected through themeasurement of the common mode voltage and the differential outputvoltage. These measurements are well known and depicted in the priorart. The transducers or sensors such as 10, 11 and 12 can be attachedvia cables of whatever length may be suitable for the application. Forexample, sensor 15 is coupled via cable 17 to module 20. To make thecabling neater and to avoid tangles, one can utilize a spring loadedreel device such as reel device 13, 16 and 18. Such reel devices arewell known and would allow for automatic retraction of the transducerswhen not in use. As seen, the reel devices associated with eachtransducer can be positioned in the housing 14 or can be positioned inthe Acquisition and Compensation electronics module 20. In any event, itis shown that reel 13 is positioned within housing 14 while reel 16 and18 are shown outside. It is of course understood that any location ofthe various reels can be employed. Thus as seen in FIG. 2, each of thetransducers is directly wired to the Acquisition and Compensationelectronic module or housing 20, which again, interfaces with a digitaloutput bus 21 which again goes to a central computer or other location.

Referring to FIG. 3, it is shown that each transducer as 10, 11, 12 and15 is connected to the Acquisition and Compensation electronics module20 via a cable with a connector on the end. Thus transducer 15 isconnected via a cable 31 to a connector module 26. Transducer 40 isconnected via cable 41 to a connector 30 which is associated with amating connector receptacle 42. As can be seen, each of the transducersas 10, 11, 12 has a connector at the end of the cable which isassociated with a mating connector on the housing 20. Thus sensor 12 hasa cable 43 which is directed to a male or female connector 44, whichmates with a connector 45, which connector 45 is mounted on the module20. In this manner, each of the sensors or transducers is connected tothe main module 20 via an associated cable with a connector on the end.

Referring to FIG. 4, there is shown another way of combining a sensor ortransducer with the electronic module 20. This would allow for anytransducer to be plugged into any channel. As seen in FIG. 4, a smallmemory chip 52 is added to the connector on each transducer. Thus asseen, the connector 51 has the memory chip 52 connected thereto,connector 51 has output pins such as 56 to 57, while the cable 58 goesto the sensor which is the transducer 59. The memory chip, for example,may be a small memory such as an EEPROM. The coefficients for correctionare stored in the transducer. The digital electronics can then readthese coefficients and use them for digital correction. This can be doneby software which the user would program in the correct coefficients foreach transducer after all the connections are made. Thus, the EEPROM orthe memory 52 stores the coefficients associated with the sensor 59. Inthis manner, when sensor 59 is plugged into a connector of theelectronic module 20, it automatically has all the coefficients storedin memory 52. Thus, the connector 51 can be inserted into any matchingconnector on the electronic module assembly 20. Thus as seen from FIG.4, the sensor 59 can be inserted into connector 42, 29 or 45 of FIG. 3and the coefficients as stored in the memory 52 would always beavailable to the electronic module 20 and be definitive of transducer59.

Referring to FIG. 5, there is shown a simple sensor configuration. Atypical sensor, which may be a full bridge includes four piezoresistorsas 61, 62, 63 and 64. The piezoresistors are semiconductor resistorswhich may be diffused or otherwise located on a thin silicon or otherdiaphragm. The diaphragm will flex upon application of a force thereto.In this manner, the piezoresistive devices are force or pressuresensitive and the resistances vary according to the force applied to theactive area of the diaphragm. Such configurations are extremely wellknown. In any event, as seen in FIG. 5, the bridge configuration 60depicted, will have various attributes or error values concerningtemperature variation as well as variations in applied pressure overtemperature ranges and so on. These coefficients involving temperatureand pressure are stored in the EEPROM 52 for each of the sensors assensor 59 and 60. It is also understood that each sensor can have itscoefficients separately stored in memory. The compensation of suchsensors regarding the prior art is well known and the assignee haspatents showing compensation of sensors for temperature and pressure.Reference is made to U.S. Pat. No. 4,192,005 entitled “COMPENSATEDPRESSURE TRANSDUCER EMPLOYING DIGITAL PROCESSING TECHNIQUES,” issued onMar. 4, 1980 to A. D. Kurtz and assigned to Kulite SemiconductorProducts, Inc., the assignee herein. That patent is the first earlyshowing of a semiconductor sensor configuration which employspiezoresistors in a bridge configuration. The patent depicts a memory,which has stored therein, predetermined values indicative of errorvoltages associated with the particular bridge circuit due toundesirable variations of temperature and pressure. The bridge circuitis coupled to digital processing circuitry which serves to access thememory at desired locations to retrieve the values stored and to processthese values in order to compensate the output signal supplied by thebridge during operation. This provides a compensated output signal trulydeterminative of the applied pressure as being compensated for theparticular error signals associated with the semiconductor sensorconfiguration and as stored in the memory. Thus, as one can ascertain,the same processing technique can be employed together with thisinvention where in one embodiment, for example, the error voltagesassociated with the particular bridge circuit due to variations oftemperature and pressure are stored in the electronic module 20. Inanother example, these error signals would be stored in the memory 52associated with the connector 51 as depicted in FIG. 4. Thus, by beingable to attach the sensors directly to the surface of the model, such asthe wing of the aircraft and so on, it would be possible to take highaccuracy measurements without sacrificing temperature or frequencyresponse. The sensors can operate at temperatures in excess of athousand degrees Fahrenheit, and the electronics can be located remotelyand one can still receive the detailed information about theaerodynamics of the surfaces being tested as well as the apparatus beingtested.

Referring to FIG. 6, there is shown a block diagram of the hightemperature, high bandwidth pressure acquisition system according tothis invention. As seen in FIG. 6, there is a plurality of sensors 70 to71. These sensors, for example, are piezoresistive Wheatstone bridgeconfigurations as shown in FIG. 5. In any event, each of the sensors hasan output connected to a multiplexer as 72. The multiplexer 72 as iswell known, can select the output of any sensor according to themultiplexing frequency. The multiplexer 72 can be controlled inoperation by the microcontroller 75. As seen in FIG. 6, the output ofthe multiplexer 72, which is the sensor multiplexer can be coupled to ananalog amplifier 73. This analog amplifier 73 is optional and dependsupon the voltage output levels of the sensor assemblies. In any event,the analog output obtained from the multiplexer indicative of the outputof each of the sensors is now converted into a digital signal via ananalog to digital converter 74. One can use one analog to digitalconverter per channel or use it with the multiplexer 72 depending on thedata rate needed. In any event, the output of the A-to-D converterprovides pressure and temperature data regarding each sensor. This datais applied to an input bus of a microprocessor or microcontroller 75,which has its own internal memory 76. Also shown is a plurality ofmemories as 80 to 81. Each memory, for example as memory 80 isassociated with a sensor as 70 while memory 81 for example, isassociated with sensor 71. The memory contains the error coefficientsfor each of the various sensors. While the memories are shownseparately, it is understood that the memories can be located in memory76 associated with the microcontroller 75. The microcontroller of coursedetermines which sensor is being scanned and therefore can go to amemory location whereby the error voltages or compensation coefficientsare stored for that particular sensor. In any event, to make matterssimple it is shown that there is memory associated with each sensor andthe output of the memories are directed via multiplexer 82. Therefore,when sensor 70 is being scanned, the output from memory 80 is directedto the microcontroller 75. The microcontroller 75 operates to compensateeach of the sensors according to the error coefficients as determinedand as stored in the various memory modules. It is of course understood,that the memory block as shown in FIG. 6 may be incorporated in theinternal memory 76 of the microcontroller 75 or for example, each of thememory modules as 80 and 81 can be stored in a connector (FIG. 4) andtherefore directed to the electronics. The microcontroller, as indicatedprovides temperature correction using coefficients from the memory ofthe microcontroller 76 or from the external memory as memories 80 and 81associated with multiplexer 82. The compensation, as indicated, isdescribed in detail in the above noted patent, namely U.S. Pat. No.4,192,005. It is further understood that various other compensationtechniques can be employed. As shown, the microcontroller 75 has ananalog output 77 which provides the analog output associated with eachsensor. The microcontroller can also convert the digital informationreceived from the analog to digital converter 74 to a different form ofdigital output to be compatible with various digital circuitry such asthe Ethernet or other digital formats. It is of course understood thatthe output of the analog to digital converter 74 is a digital signalwhich can be further processed by the microcontroller to provide anotherdigital output on the digital bus 78. The microcontroller can also takethe digital output from the analog to digital converter 74 and convertit to an analog output after compensation of temperature coefficients.It is thus seen that the above noted system enables one to make multiplepressure measurements in a rapid manner. The major aspect of the presentinvention is being enabled to attach the sensors directly to a surfacemodel and to make high accuracy measurements without sacrificingresponse in temperature or frequency.

It should therefore be apparent to one skilled in the art that there aremany embodiments of the present invention that can be ascertained andwhich employ alternate structure. Thus for example, one can employ aspecial digital circuit in lieu of microprocessor and can combine thefunctions of the multiplexers utilizing other scanning techniques. It istherefore deemed that all such alternate embodiments be encompassedwithin the spirit and scope of the claims appended hereto.

What is claimed is:
 1. A method, comprising: receiving, by a processor,from a first sensor, a first pressure signal; receiving, by theprocessor, from a second sensor, a second pressure signal; receiving, bythe processor, from a first memory, a first correction coefficient forthe first sensor; receiving, by the processor, from a second memory, asecond correction coefficient for the second sensor; modifying, by theprocessor, the first pressure signal using the first correctioncoefficient to generate a first corrected pressure signal; modifying, bythe processor, the second pressure signal using the second correctioncoefficient to generate a second corrected pressure signal; andoutputting, by the processor, the first corrected pressure signal andthe second corrected pressure signal.
 2. The method of claim 1, whereinthe processor is associated with an electronic assembly.
 3. The methodof claim 2, wherein the first memory and the second memory areassociated with the electronic assembly.
 4. The method of claim 1,wherein the first memory is a first location of a memory of theprocessor and the second memory is a second location of the memory ofthe processor.
 5. The method of claim 1, wherein the first memory is afirst location of an external memory and the second memory is a secondlocation of the external memory.
 6. The method of claim 1, wherein thefirst memory is housed with the first sensor in a first housing.
 7. Themethod of claim 1, wherein the second memory is housed with the secondsensor in a second housing.
 8. The method of claim 1, wherein a firstconnector is used to operatively couple the first sensor to theprocessor.
 9. The method of claim 8, wherein the first memory is housedwith the first connector in a third housing.
 10. The method of claim 8,wherein a first cable is used to operatively couple the first sensor tothe first connector.
 11. The method of claim 10, wherein the first cableis operatively coupled to a spring loaded reel device.
 12. The method ofclaim 1, wherein a second connector is used to operatively couple thesecond sensor to the processor.
 13. The method of claim 12, wherein thesecond memory is housed with the second connector in a fourth housing.14. The method of claim 12, wherein a second cable is used tooperatively couple the second sensor to the second connector.
 15. Themethod of claim 1, wherein each of the first sensor and the secondsensor includes a piezoresistive semiconductor sensor.
 16. The method ofclaim 1, wherein each of the first sensor and the second sensor includesa Wheatstone bridge array.
 17. The method of claim 1, furthercomprising: receiving, by the processor, from the first sensor, a firsttemperature signal associated with an ambient temperature of the firstsensor; and wherein modifying the first pressure signal using the firstcorrection coefficient includes performing temperature compensation ofthe first pressure signal using the first temperature signal and thefirst correction coefficient.
 18. The method of claim 1, whereinmodifying the first pressure signal using the first correctioncoefficient includes: performing frequency compensation of the firstpressure signal using the first correction coefficient.
 19. The methodof claim 1, further comprising: receiving, by the processor, from thesecond sensor, a second temperature signal associated with an ambienttemperature of the second sensor; and wherein modifying the secondpressure signal using the second correction coefficient includesperforming temperature compensation of the second pressure signal usingthe second temperature signal and the second correction coefficient. 20.The method of claim 1, wherein modifying the second pressure signalusing the second correction coefficient includes: performing frequencycompensation of the second pressure signal using the second correctioncoefficient.